This invention relates to conventional shackle padlocks, specifically to an improved two piece shackle mechanism for padlocks.
Historically padlocks using U shaped shackles have been found to be the most popular because of the ease and convenience of their attachment to and fit with the hasps and attachment devices with which they are used, to prevent the opening, unlatching, or coming apart of the secured elements.
The ubiquitous design, so popular for the last seventy or eighty years typically embodies a U shaped wire form that provides for the latching and locking of the shackle in the body of the padlock, and when unlocked and unlatched may be lifted so one end (the toe) is free of the body and may be pivoted around the retained end (the heel) providing sufficient clearance for the shackle to be readily engaged with the mechanism (hasp) to be secured. In the most common form this is a practical, reliable, and relatively economical solution to the problem of securing spaces or things. This idea is seen in U.S. Pat. No. 5,057 to Chambers (1847), U.S. Pat. No. 14,059 to Harrison (1856) and many others since. The utility of this concept replaced the previously popular swing style shackle seen in U.S. Pat. No. 1,243 to Nock (1839), U.S. Pat. No. 1,874 to Williams (1840) and numerous others including the overlapping swing shackle of U.S. Pat. No. 1,167,377 to Brown (1916). The lifting shackle of U.S. Pat. No. 18,169 to Yale (1857), or U.S. Pat. No. 418,359 to Troast (1889), the rotating shackle of U.S. Pat. No. 62,636 to Kelly (1867), or the shackleless padlock of U.S. Pat. No. 165,741 to Lockwood (1857), or the straight shackle of U.S. Pat. No. 438,824 to Price (1890), or the revolving shackle of U.S. Pat. No. 1,949,402 to Beaver (1934), all represent the continuing effort to achieve more effective protection by providing better, more secure padlock shackles. The intent of these early inventions continues today with clever devices to avoid the traditional shackle problems by hiding or eliminating the shackle as in U.S. Pat. No. 3,827,266 to Walters (1974), or U.S. Pat. No. 4,688,405 to Epstein (1987), or U.S. Pat. No. 4,689,975 to Dunphy et al (1987), each of which makes a contribution to improved security, but at high cost and with limited application, due to the restrictive fits inherent in the concepts.
The U shaped wire form shackle of constant circular cross section in common use today has several shortcomings that are difficult to overcome:
1. Many wire form shackles can be easily cut using commonly available tools. The traditional defense against this form of attack is to increase the diameter of the wire, with the consequent increase in the size of the lock body, or the choice of an alloy steel that can be hardened to make cutting more difficult. Each of these steps add significantly to the cost of the padlock. Another defense is the provision of a shield or shroud for the shackle to make access of cutting or forcing tools to the shackle and hasp staple difficult, but this defense is often costly and/or awkward to implement.
2. The latching mechanisms and shackles are often vulnerable to wedging, prying, and torsional attack because of the excessive space provided by the typical U shaped shackle and the sloppy fit with the hasp staple or attachment device which is often a characteristic of this arrangement.
3. The mechanical operation of lifting and pivoting the U shaped shackle is sometimes subject to malfunction caused by the environmental effects of corrosion or foreign matter (dirt and grit) within the close fitting assembly with the padlock body needed for security.
Accordingly, improvements in the design of padlocks using U-shaped shackles or other shackles to resolve the above and other shortcomings, even beyond those shortcomings solved by my U.S. Pat. No. 4,835,996 entitled "Tapered Shackle Padlock" and my U.S. Pat. No. 4,885,919 entitled "Sliding Shackle Padlock", is warranted. In addition my U.S. Pat. No. 5,146,771 entitled "Security Shield For Padlocks" and my U.S. Pat. No. 5,174,135 entitled "Tubular Hasp for Padlocks" provide alternative defenses for attacks against conventional U-shaped shackle padlocks, and my U.S. Pat. No. 4,431,220 entitled "Safety Release For Bar Lock" an emergency release for unconventional padlocks.